IDENTIFICATION AND QUANTITATION OF GENTAMICIN IN MILK USING HPLC SEPARATION AND LASER-BASED POLARIMETRIC DETECTION

The combination of reverse phase, ion pair chromatography with laser-based polarimetric detection is shown to provide unique advantages when applied to the study of gentamicin analogs. The separation procedure can separate all four of the main gentamicin analogs in a single separation system. The mass detectability for gentamicin C1a is 35 ng with this system. More importantly, the polarimetric system responds directly to the gentamicin without derivatization and can provide specific rotation information on eluting species. Individual specific rotations have been measured for the four main gentamicin analogs and found to be significantly different. This result was not predicted considering the minor structural differences which differentiate these four species. The selectivity of polarimetric detection is found to be a distinct advantage in the analysis of gentamicin in milk. The total time per analysis with this system for a milk sample is less than 30 min. © 1991.